This invention relates generally to a semiconductor processing system and, more specifically, to a semiconductor processing system having an improved lamphead.
Rapid thermal processing (RTP) systems are employed in semiconductor chip fabrication to create, chemically alter or etch surface structures on semiconductor wafers. One such RTP system, as described in U.S. Pat. No. 5,155,336, which is assigned to the assignee of the subject application and which is incorporated herein by reference, includes a semiconductor processing chamber and a heat source assembly or lamphead located on the semiconductor processing chamber.
A number of infrared lamps are located in the lamphead. During processing, infrared radiation from the lamps radiate through an upper window, light passageways and a lower window onto a rotating semiconductor substrate in the processing chamber. In this manner, the wafer is heated to a required processing temperature.
During semiconductor processing operations, the lamps operate at extremely high temperatures. Elaborate structures have been designed to conduct heat away from the lamp base. According to such techniques, the lamp base (also referred to as a xe2x80x9cpress sealxe2x80x9d) is encapsulated within a precision outer diameter stainless steel tube using a high thermal conductivity potting compound. This high precision stainless steel tube is inserted into another high precision stainless steel tube which has its outer surface (for most of its length) water cooled. This cooling mechanism causes the lamp to operate at a temperature low enough to permit long lamp life. However, this cooling mechanism can be expensive to implement, manufacture and maintain.
In general, the invention is directed to a semiconductor processing system. In one aspect, the invention features a lamphead for use in semiconductor processing. The lamphead includes a monolithic member. A plurality of lamp receptacles and reflector cavities are formed in the monolithic member. Each lamp receptacle is adapted to support a lamp and each reflector cavity is shaped to act as a reflector for the lamp.
In another aspect, the invention is directed to a process chamber having a support on which a substrate may be positioned during processing. The processing system further includes a monolithic lamphead having a plurality of lamp receptacles and reflector cavities formed therein. Each lamp receptacle is adapted to support a lamp and each reflector cavity is shaped such that the lamps direct radiant energy onto a substrate on the support.
In yet another aspect, the invention features an apparatus for processing a substrate. The apparatus includes a processing chamber having a support on which a substrate may be positioned during processing. A monolithic lamphead having a plurality of lamp receptacles and reflector cavities is part of the apparatus. The lamp receptacles are adapted to support a lamp, and the reflector cavities are shaped such that the lamps direct radiant energy onto a substrate on the support.
A plurality of coolant passages are formed in the monolithic lamphead. A reflective coating is formed on a surface of each reflector cavity. The reflective coating may comprise gold or a dielectric stack on a gold layer. A plurality of lead passages may be formed in the lamphead such that each lead passage extends between a lamp receptacle and a reflector cavity. Each lead passage is adapted to receive a lamp seal.
The semiconductor processing system may further include at least one lampholder having receptacles for the outer leads of a lamp, a ferrofluid and one or more magnets disposed about the lampholder to maintain the position of the ferrofluid near the receptacles. As such, when the lamp leads are inserted into the lampholder receptacles, the ferrofluid surrounds the leads to suppress arcing between the leads. The leads may be magnetic such that the magnets maintain the position of the lamp.
Among the advantages of the invention are the following. Reflector and lamp-wall cooling is improved by eliminating gap thermal barriers and by permitting closer proximity of coolant passages to the reflector surfaces. By eliminating the need for base and potting compounds, the use of lamps having much simpler construction is enabled. Forward-directed reflector area is increased. The method of construction of the coolant channels is simplified.
Other features and advantages of the invention will be apparent from the following detailed description, the accompanying drawings and the claims.